Charging system improvements

[ondarvr]

I have an 8hp merc on my boat as a kicker for trolling, I recently put a charging stator and rectifier on it so I can charge my batteries during the long hours of trolling with the electronics running. These standard charging systems are a little on the weak side and because it is running at, or just above idle 99% of the time, charging is minimal, but better than nothing. If I mount a second charging stator do I need to put on another rectifier, or can the two stators be wired to the same one? It looks like there is room and I may only need to fabricate a mount for one end of the stator (simple to do) and a second rectifier is no problem if needed.

Thanks

 

[Silvertip]

Re: Charging system improvements

There are two ways to do this. Combine the two outputs from the stator and feed that to the rectifier. However, the rectifier you have may not handle the current from TWO stators so the safe way to do this is to use separate stators, rectifiers, and then combine the output of the two rectifiers to feed the battery. You did say "batteries" so be aware that you are fighting a losing battle. The charging system will undoubtedly provide SOME output but hardly enough, especially at idle to even begin to keep a single battery, much less two of them topped off.

 

[j_martin]

Re: Charging system improvements

Are the stators single ended, ie 1 wire, and internally grounded, or are they isolated, ie 2 wires, neither grounded? I have something up my sleeve

 

[ondarvr]

Re: Charging system improvements

Thanks ST

The rectifier is the Radio Shack model and will handle 25 amps, so even with two stators it won't come even close to the limit.

Right now I actually only have one battery, I may install another one, but may not. I know that even with two stators it won't supply much power, but with the low cost of a second stator it can't hurt. I didn't know if the rectifier could handle pulses from two separate stators at the same time.


Sometimes I camp for several days at a time on a lake or river and even if the big motor is started, it is never run for more than just a few minutes, not even long enough to replace the power used to start it. The kicker may run for 8 hours though, and even if I do little better than breaking even on charging it will be more than worth it.

 

[ondarvr]

Re: Charging system improvements

Are the stators single ended, ie 1 wire, and internally grounded, or are they isolated, ie 2 wires, neither grounded? I have something up my sleeve

They are two wire models. Here is a link to it. I don't pay this much for them, it's just to show the type it is.

http://cgi.ebay.com/ebaymotors/MERC...035669QQ_trksidZp5197Q2em7QQitemZ320472717052

 

[j_martin]

Re: Charging system improvements

If they are positioned so that both stators line up on magnets at the same time, and are wired in series so that they are in phase, it should kick up the charging rate to max at idle. Should not hurt at high speed. Rectifier will take it, or you can get one like it that will. (200V piv) Stators should limit the current by design OK, and the battery will hold the voltage within specs.

Max current at high engine speed will not be any greater than 1 stator.

Big trick is fairly precisely lining up the second stator. If your flywheel doesn't have magnets all the way around, you're outa luck on this idea.

Then you'd need a second rectifier for the second stator. Hooked up the same way as the first.

 

[ondarvr]

Re: Charging system improvements

There are only two magnets, or at least two sets of magnets in the flywheel, mounted on the opposite side of it from each other.

Another rectifier is $3.85, so using a second one won't break the bank.

Thanks, this info helps a great deal.

 

[j_martin]

Re: Charging system improvements

If the magnets are exactly opposite, and the stators could be mounted at exactly 180? from each other, my series scheme would work.

 

[ondarvr]

Re: Charging system improvements

Will two separate and independent stators jump the voltage up higher, or two high?

I can always put a manual switch in line to disable one stator if voltage at higher RPM's becomes an issue.

 

[ondarvr]

Re: Charging system improvements

If the magnets are exactly opposite, and the stators could be mounted at exactly 180? from each other, my series scheme would work.

They are 180, but the ignition stator is in that location.

 

[j_martin]

Re: Charging system improvements

The stators are current limited by design. It's a function of the amount of iron in the core and the turns on the coils. If it charges at idle, the open circuit voltage is at least 15 volts. If idle is 1000 rpm, and WOT is 5000 rpm the open circuit voltage of the stator would be 75 volts at WOT. The battery limits it to 15 volts or so.

Two in series would operate the same way, just put a higher reverse voltage on the rectifier. As long as the rectifier can take it, all else should be a go. They are available up to about 1000 volt PIV, with 400 or 600 being common.

The peak current available at WOT would not be any more than a single stator, but the charging voltage and current at low speed should be greatly enhanced.

 

[j_martin]

Re: Charging system improvements

They are 180, but the ignition stator is in that location.

Bummer.

Another idea would be to use a capacitor on each rectifier and stack them up. It's probably not worth the effort as it would take fairly large capacitors.

Another idea would be to use the secondary of a 24V center tapped transformer as an autotransformer on each stator, doubling the voltage at half the current. Same effect as stacking the stators would have been.

 

[ondarvr]

Re: Charging system improvements

I went out and pulled the flywheel while you were posting.

It will be a tight fit, "if" I can fit another stator in I will need to grind a bit off of the first charging stator, ignition stator and the new one I want to put in., I need about 3/16 of an inch more room. This material only needs to be removed from the mounting portion where the bolts go through.

 

[j_martin]

Re: Charging system improvements

I went to bed.....................

You should see the mounting plate I had to make to put 40 amp dual regulators on a 16 amp XR4. Everything fits but the flywheel cover.